This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on patent application Ser. No. 2001-63986 and 2002-60549 filed in KOREA on Oct. 17, 2001 and Oct. 4, 2002, which is herein incorporated by reference.
The present invention relates to a process for preparing 3-hydroxyesters by carbonylating an epoxide derivative. More specifically, the present invention relates to converting an epoxide derivative into 3-hydroxyesters through reaction with carbon monoxide and alcohol in the presence of a catalyst system consisting of a cobalt catalyst and a promoter, followed by the efficient separation of the catalyst system from the resulting reaction product so as to recycle the catalyst system.
Epoxide derivatives can be readily converted into a difunctional compound via carbonylation so that they can be used as an intermediate compound for preparing useful organic compounds. Particularly, since a 3-hydroxyester derivative has two functional groups, it has been known that it can be used as solvents, resins and coating materials. Further, it is possibly used as a raw material for pharmaceutical compounds or as an intermediate for organic synthesis due to its easy convertibility into other compounds and can also be used as an intermediate for synthesis of alkanediols, which are the raw material for polyesters. Such alkanediols, particularly 1,3-alkanediols have been generally prepared by hydroformylating an epoxide derivative into a 3-hydroxyaldehyde derivative and then hydrogenating the 3-hydroxyaldehyde derivative to convert aldehyde group thereof into alcohol group. This process is fully described in U.S. Pat. Nos. 5,770,776, 5,723,389 and 5,731,478 by Shell Co.
On the other hand, the preparation of 3-hydroxyaldehyde derivatives in a condition of relatively low temperature and low pressure with high selectivity has been accomplished by the use of a cobalt catalyst in conjunction with a promoter, a phosphine oxide ligand. However, this technique has been found to be troublesome in that the recovery and recycling of the catalyst is difficult in the presence of such promoter.
To solve these problems, U.S. Pat. No. 5,770,776 discloses a process for preparing 1,3-propandiol, comprising: contacting ethylene oxide with carbon monoxide and hydrogen in a non-aqueous solvent in the presence of a catalyst system consisting of a cobalt catalyst and an alternative promoter, i.e., a metal complex or a ligand other than the phosphine oxide ligand; adding an aqueous solution to the resulting intermediate product to obtain a first aqueous phase product and a first organic phase material; isolating the first aqueous phase product from the first organic phase material; adding a non-aqueous solvent to the first aqueous phase product to obtain a second aqueous phase product and a second organic phase material; isolating the second aqueous phase product from the second organic phase material; and recycling the first and the second organic phase materials to the first step, wherein the isolated second aqueous phase product containing 3-hydroxypropanal is contacted with hydrogen in the presence of a hydrogenation catalyst and the resulting 1,3-propandiol is finally recovered.
U.S. Pat. Nos. 5,723,389 and 5,731,478 disclose a process for preparing alkanediols, comprising: contacting ethylene oxide with carbon monoxide and hydrogen in the presence of a catalyst system consisting of a cobalt catalyst and an alternative promoter, i.e., a metal complex or a ligand other than the phosphine oxide ligand in a non-aqueous solvent; adding an aqueous solution to the resulting intermediate product to obtain an aqueous phase product and organic phase materials; isolating the aqueous phase product from the organic phase materials; contacting the aqueous phase product containing 3-hydroxyaldehyde with hydrogen in the presence of a hydrogenation catalyst, and recovering the resulting alkanediols.
U.S. Pat. Nos. 5,981,808 and 5,986,145 propose a process for preparing 1,3-propandiol, comprising contacting ethylene oxide with carbon monoxide and hydrogen in the presence of a catalyst system consisting of a cobalt catalyst and an alternative promoter, i.e., a metal complex or a ligand other than the phosphine oxide ligand in a non-aqueous solvent; adding an aqueous solution to the resulting intermediate product to obtain an aqueous phase product and an organic phase material; recycling the organic phase material to the first step, wherein the water-soluble cobalt catalyst is removed from the final reaction product, 3-hydroxypropanal, by contacting the aqueous phase product comprising 3-hydroxypropanal contaminated with the cobalt catalyst with oxygen or oxygen-containing gas(e.g., air) at 5xcx9c55xc2x0 C. for 1xcx9c15 minutes in the presence of an adequate amount of organic acid under a pressure of 50xcx9c200 psig by carbon monoxide to convert the water-soluble cobalt catalyst into a water-insoluble cobalt compound, which in turn is removed out by using an ion-exchange resin. Nevertheless, the remaining aqueous phase has been found to include a considerable amount of cobalt in addition to 3-hydroxypropanal.
Meanwhile, U.S. Pat. No. 4,973,741 teaches that xcex2-hydroxypropionate can be obtained by reacting carbon monoxide, hydrogen, ethylene oxide, and primary alcohol or benzyl alcohol together in the presence of a catalyst system consisting of rhodium and a promoter of Va family. However, this technique is also disadvantageous in that the yield of methyl 3-hydroxypropionate is only 66% in spite of the use of the expensive catalyst and a large amount of byproducts are produced.
According to another techniques, the conversion rate of an epoxide to a xcex2-hydroxyester through hydroesterification has been reported to be only 40xcx9c60% (see: for example, Dalcanali, E., and Foa. M., Synthesis (1986) 492; Heck, R. F., J. Am. Chem. Soc. (1963) 85, 1460; and Eisenmann, J. L., Yamartino, R. L., Howard, Jr. J. F., J. Org. Chem. (1961) 26, 2102). It is surmised that such a low yield is due to the spontaneous isomerization of the starting material.
U.S. Pat. Nos. 5,310,948 and 5,359,081 disclose that a reaction of an epoxide with carbon monoxide up to 60 atm in the presence of a catalyst system consisting of cobalt and a pyridine derivative, particularly 3-hydroxypyridine, yielded primarily xcex2-propiolactone, while 3-hydroxymethylpropionate may be produced according to the reaction condition. In these prior arts, however, there is no description on the recovery or recycling of the cobalt catalyst.
U.S. Pat. No. 6,191,321 describes a process for preparing 1,3-propandiol through the hydrogenation of 3-hydroxymethyl propionate. This technique also has a very low production yield and provides no description on the recovery and recycling of cobalt, which are merely supposed to be conducted in an aqueous phase.
In the preparation of 1,3-alkanediols, when 3-hydroxyaldehyde forms as an intermediate as in the prior arts, the inherent instability of the aldehyde causes the formation of oligomers as well as byproducts such as acetals, which consequently deteriorates quality of the final product. In addition, such complicated recovery and recycling of the cobalt catalyst remain to be solved.
As a part of effort to solve these problems with the prior arts, the present inventors already proposed a novel process for preparing 3-hydroxyesters and 1,3-alkanediols in Korean Patent Application No. 2001-1784. According to this technique, reaction product and catalyst are separated from each other by the vacuum distillation or the extraction of the catalyst into an aqueous phase, and the catalyst thus separated can be reused.
A feature of the present invention is to provide a novel process for preparing 3-hydroxyesters by reacting an epoxide derivative with carbon monoxide and alcohol in the presence of a catalyst system consisting of a cobalt catalyst and optionally a particular promoter to efficiently produce a 3-hydroxyester, followed by the isolation of the catalyst system form the reaction mixture in order to reuse it in another cycle of 3-hydroxyester preparation.
Another feature of the present invention is to provide a simplified technique for isolating the cobalt catalyst system without requiring intricate equipments or procedures, which allows minimum production cost to be incurred in the preparation of desired 3-hydroxyesters.
Still another feature of the present invention is to provide a novel process for preparing 3-hydroxyesters, comprising:
(a) reacting an epoxide derivative with carbon monoxide and alcohol in a solvent at a temperature of 30xcx9c150xc2x0 C. under a pressure of 50xcx9c3000 psig by using a catalyst system consisting of a catalytic amount of a cobalt compound and optionally an effective amount of a promoter to produce a 3-hydroxyester or a derivative thereof;
(b) separating the resulting product and the solvent from the cobalt compound and the promoter in a stripping column at a temperature of xe2x88x9230xcx9c200xc2x0 C. in an atmosphere of a stabilizing gas; and
(c) recycling a part or all of the separated cobalt compound and promoter to the step (a) and repeating the steps (a) through (c).
Other feature and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.